The U.S has sanctioned Russia over alleged interference of Russian hackers in the recently concluded election to give Donald Trump an edge.

President Barack Obama on Thursday ordered the expulsion of 35 Russian suspected spies and imposed sanctions on two Russian intelligence agencies over their involvement in hacking U.S. political groups in the 2016 presidential election.

The measures, taken during the last days of Obama’s presidency, mark a new post-Cold War low in U.S.-Russian ties and set up a potential flashpoint between incoming President-elect Donald Trump and fellow Republicans in Congress over how to deal with Moscow.

Obama, a Democrat, had promised consequences after U.S. intelligence officials blamed Russia for hacks intended to influence the 2016 election. Officials pointed the finger directly at Russian President Vladimir Putin for personally directing the efforts and primarily targeting Democrats, who put pressure on Obama to respond.

“These actions follow repeated private and public warnings that we have issued to the Russian government, and are a necessary and appropriate response to efforts to harm U.S. interests in violation of established international norms of behavior,” Obama said in a statement from Hawaii, where he is on vacation.

“All Americans should be alarmed by Russia’s actions,” he said.

It was not clear whether Trump, who has repeatedly praised Putin and nominated people seen as friendly toward Moscow to senior administration posts, would seek to roll back the measures once he takes office on Jan. 20.

Trump has brushed aside allegations from the CIA and other intelligence agencies that Russia was behind the cyber attacks. He said on Thursday he would meet with intelligence officials soon.

“It’s time for our country to move on to bigger and better things,” Trump said in a statement.

“Nevertheless, in the interest of our country and its great people, I will meet with leaders of the intelligence community next week in order to be updated on the facts of this situation,” he said, without mentioning Russia.

The Kremlin, which denounced the sanctions as unlawful and promised “adequate” retaliation, questioned whether Trump approved of the new sanctions. Moscow denies the hacking allegations.